What is dark matter and dark energy? Is dark matter a denser version of air in space?

Dark matter is the molasses of the cosmos, as I understand it, and it can’t influence gravity. I understand that it is a bit like steam in an engine, keeping the train in motion. Correct me if I’m wrong.

Comments:

Dark matter is a lot like normal matter, but with one crucial exception: it doesn’t interact with the electromagnetic force. This means there is no electromagnetic attraction or repulsion, no interaction with light or any other form of EMR. Of course, the only reason we think this is because we can’t see it. Dark matter makes up for a huge percentage of the universe’s mass, and yet…we can’t see it. We can however, see it’s effects.

Dark matter still interacts with and exudes the gravitational force, and we can see this effect in a phenomenon known as Gravitational Lensing. Essentially, when we look into the sky and take pictures (with the Hubble Telescope), we can see that some galaxies are curved, or lensed. This is caused by the light from these galaxies being ‘bent’ by a strong gravitational field on the way to Earth. We can’t actually see what’s causing these fields, and they are presumed to be caused by the invisible dark matter.

Dark Energy is quite different from Dark Matter. It makes up for around 73 percent of the total mass-energy of the universe, and yet we still have no direct evidence of it. It is believed to not interact with any of the fundamental forces other than gravity however, and is also believed to possess a strong negative pressure. This presumed pressure is the reason we attribute the universe’s expansion to dark energy.

Also, whilst dark matter is known to form clumps and clusters throughout the universe, dark energy is spread evenly throughout space. In all honesty though, that’s about as much as we know about dark energy. It’s a very new concept in physics, and is very difficult to study. But it could answer a lot of questions that need to be answered (quantum gravitation, for one).

Dark matter and dark energy are, firstly, purely hypothetical. There are no means to observe them, today. They are a result of the Big Bang Theory. To support the BBT, the theory of inflation was necessary and to support inflation, something like Dark Matter and Dark energy were necessary. This is so because inflation was shown to be slowing down after the Big Bang and something with great gravitational pull was needed to explain the slowing down. That was where these two concepts arose. They are perfect Planck Black Bodies(With no electromagnetic radiation). Dark Matter is said to have constituted 23% of the universe, while Dark Energy 72%. Do remember though that they are purely hypothetical, i.e., there is no reason for them to exist if it weren’t for the Inflation Model. However, if they were to exist, they would be sub-atomic particles that just haven’t been detected in LHCs. If they exit, we would find them someday. After all, the Higgs and the Neutrino were also similar, and we found them eventually.